For that type of number, yes, it’s the 39th week of 1983. However, Heat Controller also has a number type where the first three or four digits are the month and year. Usually it will be one long 11- or 12-digit number.
You wil also find some where the second through fourth digits are the year (single digit) and the month (two digits), as well as second through fifth digits being the year and month.
And then there’s also a number where the first two digits are the year.